Baking & Snack - May 2004 - 77

ANALYSIS

WHAT IS PROXIMATE ANALYSIS?
In all the nutritional information that appears
on labels, the information of main interest to
consumers is the Proximate Analysis: moisture,
protein, fat, ash, ﬁber and carbohydrates.
Total Carbohydrates: The percentage of total carbohydrates equals 100: % moisture + % protein +
% fat + % ash. The Nutrition Facts label required by
the Nutritional Labeling and Education Act (NLEA)
shows "Total Carbohydrates," "Sugars" and "Dietary
Fiber." The implication is that Total Carbohydrates
minus (Sugars + Dietary Fiber) represents complex
carbohydrates, that is, starch and dextrins.
Sugars are extracted from the sample overnight with hot alcohol. Then any sucrose present
is hydrolyzed with acid. The total amount of
reducing sugar is measured by one of the ofﬁcial
methods. The analytical value is reported as
sugars equivalent to glucose.
Protein: The amount of protein in a food is
not measured directly. Instead the sample is
oxidized, using sulfuric acid (Kjeldahl method)
or oxygen gas (Dumas method). The nitrogen
present is converted to ammonia (Kjeldahl)
or nitrogen gas (Dumas). These are measured
by distillation and titration or by volumetric
measurement, respectively. Finally the protein
concentration is calculated as the amount of
nitrogen (N) times some factor.
For wheat proteins, this factor is 5.7 (determined by actually measuring N in carefully
puriﬁed gluten). For milk products, the factor
is 6.38, and for protein from other sources
(for example, soy protein), the factor used is
6.25. When determining the protein in a bread
containing a signiﬁcant amount of milk or soy
protein fortiﬁcation, the calculation of N x 5.7
might underestimate the actual protein level.
On the other hand, there are other nitrogenous
components in foods, such as nucleic acids and
nitrates. These give an overestimation of the
protein content, but the error is generally small.
Rapid methods of protein measurement -
NIR, dye-binding - are used but are calibrated
by reference to Kjeldahl or Dumas determination.
Fat: The concentration of fatty acids is calculated as equivalent triglycerides. The sample
is digested with 8N hydrochloric acid. Then the
free fatty acids are extracted with hexane and
converted to methyl esters. These are separated
by gas chromatography (GC), and the amount of
each class of fatty acid (saturated, monounsaturated, polyunsaturated) in the original sample is
determined. These are expressed as the weight of
equivalent triglyceride (nearly equal to the weight
of the methyl esters) and reported as fat content.
Nonpolar lipids may be extracted from the
sample with hexane (Soxhlet method), but extraction of polar lipids such as emulsiﬁers is incomplete. Thus, determining fat by the Soxhlet method
underestimates the amount of fatty acids present,
sometimes by as much as 50%. Acid hydrolysis
and methyl ester GC is the only ofﬁcial method for
determining fat content of a baked food.
Ash: The weighed sample is heated in a
mufﬂe furnace at 1,000°F to 1,100°F (550°C to
600°C) until all organic material is burnt off. The
pan containing residue is cooled and weighed.

Fiber: The undigestible organic portion of foods
is labelled as dietary ﬁber. This is measured by
digesting the sample with protease and starchdigesting enzymes, then collecting, drying and
weighing the undigested components. Simple
ﬁltration of the digest gives insoluble dietary ﬁber,
while gums (soluble dietary ﬁber) are precipitated
by the addition of alcohol. If alcohol is added to the
digest before the ﬁrst ﬁltration, both fractions are
measured at the same time, as total dietary ﬁber.

Moisture: The moisture level in a food product is
determined by placing an amount of sample in a pan,
heating for one hour at 266°F (130°C), followed by
cooling and weighing. If the sample moisture is more
than 16% (bread, sweet goods, etc.), it is partially
dried before grinding and oven drying.
Numerous instruments for rapidly determining moisture are available. These use infrared or
microwave heating, NIR spectrophotometry or
dielectric resistance.

Your
Dream Ingredient
Are you dreaming of a cost
effective ingredient that brings
all the function of eggs to
your products - without the
handling and sanitation
nightmares? Eggstend® is a
dairy based product that
makes replacing eggs in your
formulation a dream come true.
Eggstend® replaces liquid,
frozen and dried whole egg
products. This all-dairy egg
replacement powder allows you
to focus on your product, while
avoiding handling issues such as
breakage, refrigeration, freezing
or thawing. And there are no
egg allergen concerns.
Eggstend® is ideal in bakery
products, fresh pastas and
flavored salad dressings. To
find out more, contact Parmalat
at 1.877.891.0811 or via email
at ingredientsinfo@parmalat.ca.

www.parmalat-ingredients.com
For more information, see Page 162

May 2004 / BAKERS PRODUCTION MANUAL / 77

http://www.parmalat-ingredients.com

Baking & Snack - May 2004

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